In this paper, we use administrative records from the U.S. Border Patrol to examine how penalizing illegal border crossing affects recidivism in the apprehension of undocumented migrants at the U.S.-Mexico border. Over 2008 to 2012, the Border Patrol rolled out a Consequence Delivery System, which increased the fraction of apprehended border crossers subject to administrative or criminal sanctions from 15% to 85% percent. By matching fingerprints across apprehension records, we detect if a migrant apprehended by the Border Patrol is subject to penalties and if he is re-apprehended at a later date. Exploiting day-to-day variation in the capacity of the Border Patrol to levy sanctions during the rollout phase, we estimate strong effects of penalties on the likelihood that an apprehended migrant re-attempts illegal entry and is recaptured. Exposure to (milder) administrative penalties reduces the 3-month and 18-month re-apprehension rates for male Mexican nationals by 6.6 and 4.6 percentage points, off of baseline rates of 22.6% and 24.2%; exposure to the full set of penalties reduces these re-apprehension rates by 8.1 and 6.1 percentage points. The estimated magnitudes imply that the rollout of the CDS can account for 28 to 44 percent of the reduction in re-apprehension rates over 2008 to 2012. Further results suggest that our estimated impacts of sanctions on recidivism in apprehensions may understate the impact of sanctions on recidivism in attempted illegal entry. [Emphasis added.]